Many of such cooling fans have a basic structure in which a plurality of blades protruding outward in a radial direction are installed at a boss section connected to a rotary drive source such as an engine or an electric motor, and the blades are rotated by power of the rotary drive source to blow air to a cooled object.
Here, in such a cooling fan, while it is well known that fan efficiency is advantageously increased when the thickness of the blade is thinned, when the thickness of the blade is thinned, the blade is likely to be bent and cause flapping upon rotation.
For this reason, as a cooling fan configured to accomplish both of suppression of the flapping and thinning of the blade, a configuration in which the vicinities of the end sections outside in the radial direction of the plurality of blades are connected by a cylindrical ring member is proposed (for example, see Patent Document 1).